Commutating SOA capability of power DMOS FETs

Measured characteristics are presented of the fast-recovery diode in a DMOS FET, its commutating safe operating area (CSOA) limitations, and the physical model of its operation and failure. Device optimization to improve the CSOA performance is discussed and demonstrated with a new generation of DMOS FETs which are specially developed for industrial motor control applications. A standard 500 V DMOS FET was electron irradiated to enhance the diode recovery speed. A half-bridge circuit was used for measurements. The lower DMOS FET is driven by a gate circuit to switch an inductive load. Upon turn-on of this device, the forward diode current of the device under test (DUT) is forced to zero and reverse recovery of the diode begins. Thus, the device under test DUT is subjected to stress conditions similar to those which occur in actual applications.<>